Greater supply of Patagonian-sourced detritus and transport by the ACC to the Atlantic sector of the Southern Ocean during the last glacial period
Reconstructing past detrital flux and provenance in the SouthernOcean provides information about changes in source regions associated with climate variations and transport pathways. We present a LastGlacial Maximum (LGM) to Holocene comparison of 230Th normalised fluxes combined with sediment provenance data (Pb, Nd and Sr isotopes) from a latitudinal core transect in the eastern Atlanticsector of the SouthernOcean (ODP Leg 177 cores). We compare the radiogenic isotopic composition (IC) of detritus in these cores to that of cores proximal to potential source areas.We observe a well-defined latitudinal Holocene gradient in both detrital flux and provenance of sediment. High detrital fluxes in the north are associated with terrigenous material derived from southern Africa, while low detrital fluxes in the south are associated with supply from southern South America, West Antarctica and the South Sandwich Islands. The data suggest that this well-defined Holocene gradient in detrital flux and sediment provenance is controlled by the flow of the Antarctic Circumpolar Current (ACC) and the position of its frontal zones. The LGM is characterised by 2 to 6 times higher than modern detrital fluxes at most ODP Leg 177 sites. The LGM detrital fluxes do not show a latitudinal trend and suggest a greatersupply of glaciogenic detritussourced from southern South America. GlacialPatagonian outwash sediments (< 5 μm fraction) were analysed and compared to the bulk compositions of the marine sediments. The Pb IC of the Patagonian sediments is very similar to the glacial IC of sediments in the Scotia Sea and at ~ 49° S latitude in the eastern Atlanticsector. We propose that the glacial IC of sediments is controlled by increased delivery of Patagoniandetritus initially supplied by glaciers and then transported at depth via the ACC.
Authors: Noble, Taryn L., Piotrowski, Alexander M., Robinson, Laura F., McManus, Jerry F., Hillenbrand, Claus-Dieter, Bory, Aloys J.-M.